1. Field of the Invention
The present invention relates to an electro-static discharge protection device that protects electronic equipment from breakage due to electro-static discharge.
2. Description of the Related Art
To date, electro-static discharge protection devices (ESD protection devices) for suppressing breakage of electronic equipment due to electro-static discharge (ESD) have been widely used.
For example, International Publication No. 2010/067503 describes an ESD protection device including a ceramic multilayer substrate, at least a pair of discharge electrodes disposed on the ceramic multilayer substrate and opposed to each other with a distance therebetween, and outer electrodes disposed on the surface of the ceramic multilayer substrate and connected to the discharge electrodes, wherein a supporting electrode composed of a dispersed metal material and a semiconductor material is included in a region that provides a connection between the pair of discharge electrodes. The ESD protection device described in International Publication No. 2010/067503 includes the supporting electrode that provides a connection between the discharge electrodes and, thereby, ESD characteristics are easily adjusted and stabilized.
In addition, International Publication No. 2011/040435 describes an ESD protection device including a ceramic base material including a glass component and, inside the ceramic base material, opposed electrodes including one of the opposed electrodes and the other of the opposed electrodes, which are disposed such that an end portion of the one and an end portion of the other are opposed to each other with a distance therebetween, and a discharge supporting electrode, which is connected to both of the one of the opposed electrodes and the other of the opposed electrodes of the opposed electrodes and which is arranged so as to span from the one of the opposed electrodes to the other of the opposed electrodes, wherein a seal layer that prevents intrusion of a glass component from the ceramic base material into the discharge supporting electrode is disposed between the discharge supporting electrode and the ceramic base material.
International Publication No. 2010/067503 and International Publication No. 2011/040435 describe ESD protection devices in which a pair of discharge electrodes are opposed to one another in a hollow portion located in the ceramic base material. In the case where a voltage of a certain value or higher is applied to the ESD protection device having such a configuration, aerial discharge and creepage discharge occur in a portion in which the discharge electrodes are opposed to each other. Therefore, the discharge characteristics of the ESD protection device are determined depending on the clearance between the discharge electrodes and the volume of the hollow portion. Consequently, in order to stably provide predetermined ESD protection performance, it is effective to accurately set the distance between the discharge electrodes and the volume of the hollow portion.
Movement of electrons between the discharge electrodes is facilitated by disposing the discharge supporting electrode in the portion in which the pair of discharge electrodes are opposed to each other so as to efficiently generate a discharge phenomenon and, thereby, the ESD response can be improved. Discharge supporting electrodes containing metal materials and/or semiconductor materials are known (i.e., International Publication No. 2010/067503). However, where the discharge supporting electrode contains silicon carbide (SiC) as a semiconductor material, the volume of the hollow portion may be expanded by gas generation in the production process of the ESD protection device, and a problem of the hollow portion being deformed may occur. Such deformation of the hollow portion may cause the occurrence of cracking and the occurrence of peeling of the discharge electrode in the ESD protection device. Peeling of the discharge electrode causes an increase in distance between the discharge electrodes and, as a result, the discharge characteristics of the ESD protection device may be degraded. Further, discharge characteristics may not be exhibited in some cases.